1. Field of the Invention
The present invention relates to an interlock switch mechanism and an image formation device utilizing the same, more particularly relates to an interlock switch mechanism having a stroke extension mechanism and an image formation device including the interlock switch mechanism.
2. Description of the Related Art
FIG. 8 illustrates a conventional interlock switch mechanism 200. As shown in FIG. 8, the interlock switch mechanism 200 contains a first link rod 201, a spring 206, a second link rod 203, a rotation part 204, and an action part 205.
The first link rod 201 may swing in a vertical plane by centering on a supporting point 201A. The spring 206 may cause the first link rod 201 to return to an initial position (i.e., a position where a switch 202 is turned off). The second link rod 203 is supported by a supporting shaft 201B disposed at the end 201C of the first link rod 201 so that two ends 203A and 203B of the second link rod 203 may swing in the vertical plane. The end 203A of the second link rod 203 faces an actuator 202A of the switch 202. The rotation part 204 is shaped like a cam, and may rotate with respect to a rotation shaft 204B. Furthermore the rotation part 204 has an arc portion 204A1 with a predetermined radius, a contacting portion 204A2, and a coil spring 204C for causing the rotation part 204 to return to the initial position. The arc portion 204A1 may touch the other end 203B of the second link rod 203. The action part 205 is disposed at another end 201D of the first link rod 201.
FIG. 9 illustrates a conventional image formation device 100. The above described interlock switch mechanism 200 is used in the image formation device 100. As shown in FIGS. 8 and 9, the image formation device 100 contains a housing 100A, a first door 24, a second door 25, a first movable part 300, and a second movable part 301. Here it should be noted that the two movable parts 300 and 301 are shown in FIG. 8.
A first boss 24a is disposed on the inner surface of the first door 24. A second boss 25a is disposed on the inner surface of the second door 25. A first opening 100A1 and a second opening 100A2 are disposed on side walls of the housing 100A, facing the bosses 24a and 25a, respectively. The two bosses 24a and 25a may be inserted into the openings 100A1 and 100A2, respectively. The first movable part 300 is disposed inside the image formation device 100, and may be pushed by the first boss 24a. The second movable part 301 is disposed inside the image formation device 100, and may be pushed by the second boss 25a. The first movable part 300 faces the contacting portion 204A2 of the rotation part 204 in the interlock switch mechanism 200, and the second movable part 301 faces the action part 205 in the interlock switch mechanism 200.
In a process of closing the first door 24 of the image formation device 100, the first boss 24a pushes the first movable part 300. Then the first movable part 300 overcomes an elastic force of the coil spring 204C so as to push the contacting portion 204A2 of the rotation part 204 in the interlock switch mechanism 200. In this way, the arc portion 204A1 touches the other end 203B of the second link rod 203.
In a process of closing the second door 25 of the image formation device 100, the second boss 25a pushes the second movable part 301. Then the second movable part 301 overcomes an elastic force of the spring 206 so as to push the action part 205 in the interlock switch mechanism 200. In this way, the first link rod 201 swings so that its end 201C moves upward, and then the supporting shaft 201B of the second link rod 203 moves upward too.
On the other hand, since the other end 203B of the second link rod 203 is stopped by the arc portion 204A1 of the rotation part 204, the end 203A of the second link rod 203 moves upward so as to approach the actuator 202A of the switch 202. When the first door 24 and the second door 25 are closed fully, the end 203A of the second link rod 203 activates the actuator 202A of the switch 202.
The switch control accuracy of the conventional interlock switch mechanism 200 is relatively low. In a case where the first door 24 or the second door 25 is opened by a relatively small angle (for example, less than 25 degrees), there is a problem that the switch 202 cannot be effectively turned off, i.e., is still in a turn-on state.